Nanoscale electromechanical coupling in atomically thin materials

非技术描述：材料的结构变形，如弯曲或起皱，会导致其电子性能的巨大变化。该项目在所谓的二维材料（如二硫化钼和二硒化钨）中探索了这些效应，这些材料只有几个原子厚，因此由于其极端的机械灵活性，不可避免地会遭受结构变形。该研究的重点是使用先进的显微镜技术来测量和分析二维材料中通过压电等效应产生的变形所产生的电荷和电压分布。这些效应在基于这些材料的计算和通信设备和技术中起着核心作用，包括量子信息处理的拟议方法。这方面的研究与教育和外联活动密切相关。特别是，一项以设计和建造简单的光学显微镜为重点的活动，该显微镜基于乐高积木或三维打印组件，结合极其便宜、容易购买的塑料光学组件，为不同人群的小学生提供了一个新的窗口，让他们了解成像在探索世界中的力量，以及现代制造技术，如三维打印。技术描述：本项目重点研究原子薄过渡金属二硫化物材料中的压电和挠性机电耦合现象。强调三个主要方向。首先，该项目探索了机电耦合的表征和分析，在平面内和面外方向上，在单层到多层厚的过渡金属二硫化物中，使用压电响应力显微镜。其次，该项目使用剥离和层转移技术来创建与相应的大块材料相比对称性降低的双层过渡金属二硫族化物同质结和异质结，以通过控制双层范德华同质结构和异质结构的组成和对称性来评估工程机电响应的可能性。这些结构的近端探针表征提供了对具有不同层组成和旋转排列的双层中与局部对称性相关的纳米级机电响应的见解。第三，该项目将计算模型与实验测量相结合，以分析基于原子级薄过渡金属二硫化物材料的功能电子和光子结构在纳米尺度上的机电耦合的影响，其中存在高度不均匀的应变分布。通过在纳米尺度上探索与压电和柔性电有关的基本问题，该研究通过直接实验表征与计算建模相结合，为这些效应的性质、大小和技术含义提供了新的信息和见解。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical Description: Structural deformation of materials, such as bending or wrinkling, can lead to dramatic changes in their electronic properties. The project explores these effects in so-called two-dimensional materials, such as molybdenum disulfide and tungsten diselenide, that are only a few atoms thick, and that therefore inevitably suffer from structural deformation due to their extreme mechanical flexibility. The research focuses on using advanced microscopy techniques to measure and analyze electric charge and voltage distributions that arise in the presence of deformations in two-dimensional materials through effects such as piezoelectricity. These effects play a central role in devices and technologies for computing and communications that are based on such materials, including proposed approaches for quantum information processing. Research on this topic is closely integrated with activities in education and outreach. In particular, an activity focusing on design and construction of simple optical microscopes based on Legos or three-dimensional printed components combined with extremely inexpensive, readily purchased plastic optical components provides diverse populations of elementary school students with a new window into both the power of imaging in exploring their worlds, and modern manufacturing technologies such as three-dimensional printing.Technical Description: The project focuses on fundamental studies of electromechanical coupling phenomena - piezoelectricity and flexoelectricity - in atomically thin transition metal dichalcogenide materials. Three primary directions are emphasized. First, the project explores characterization and analysis of electromechanical coupling, in both in-plane and out-of-plane directions, in mono- to several-layer thick transition metal dichalcogenides using piezoresponse force microscopy. Second, the project uses exfoliation and layer transfer techniques to create bilayer transition metal dichalcogenide homojunctions and heterojunctions with reduced symmetry compared to the corresponding bulk materials to assess possibilities for engineering electromechanical response via control over the composition and symmetry of bilayer van der Waals homostructures and heterostructures. Proximal probe characterization of these structures provides insight into nanoscale electromechanical response associated with local symmetry in bilayers with different layer compositions and rotational alignments. And third, the project combines computational modeling with experimental measurements to analyze the implications of electromechanical coupling at the nanoscale for functional electronic and photonic structures based on atomically thin transition metal dichalcogenide materials in which highly inhomogeneous strain distributions are present. By exploring fundamental issues pertaining to piezoelectricity and flexoelectricity at nanoscale dimensions, the research provides new information about and insights into the nature, magnitude, and technological implications of these effects through direct experimental characterization combined with computational modeling.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.